Why do we do water changes?

[geowashlaw]

I religiously change 20% of my water every other week ... but I don't know why I do it ... especially since I test my tank regularly (at least every other day) and always have 0 ammonia, 0 nitrates and 0 nitrites ... just a noob question, but what is the reason for the w/c?

[smaug]

In the wild there water turns over in the order of millions of gallons an hour.In our homes they are essetially swimming in there own filth for days on end.The solution to pollution is dillution.

[Wild Turkey]

Other than removing nitrates, it removes impurities that have made their way into the tank and fixes common problems before they start by taking old water out and bringing new, fresh water in.

New water also contains fresh nutrients for live plants. There are ton of other reasons but those are a few.

Edit:
I like the way smaug put it.

The thing is, if you werent already doing those water changes, you might not have zero nitrate ;)

[geowashlaw]

I see ... I knew there had to be a reason, I just couldn't figure out what it was ...

[Northernguy]

20% every other week is not enough to make a difference.Well very little.
At least if you are going to have a slack schedule than change at least 50%.
Your fish will sure appreciate it.:22:
They really do need it.Just because it is testing perfect does not mean it is.
Your fish will all of a sudden become ill or break out with something and you will be scratching yor head wondering what happened.

[Fishalicious]

Simple - nothing likes to swim around in it's own pee :hmm3grin2orange:

[NickFish]

In addition to everything being said above, fish love to "eat" new water.

Fish can absorb nutrients through their skin, and replacing water brings in lots of electrolytes, vitamins, and minerals.
Of course, the main reason is to get rid of waste. Plain and simple. Just because it can't be tested doesn't mean it isn't there

[Adrian]

Really???? I thought I was changing my water to feed my indoor plants and to use it as a fertalizer for my garden. Hmmm, guess having clean water for fish would be good too. (Just kidding) I know it is a serious problem if the water doesn't get changed. One thing many people don't realize, is that by doing water changes, also removes excess phospates. That is one of the main reasons for algae outbreaks, and harder to test for, as most people don't even bother to test for it.

[Kaga's Kritters]

if you have 0 nitrates all the time then i would be concerned......i had that happen and then realized i was doing the test wrong. if you are using the test tube and bottle test than make sure you follow the instructions carefully. you have to shake this test to make it work right. if you don't it never gives a real reading. if you are using the strips then i would suggest getting the bottled tests, they are more accurate.

[geowashlaw]

if you have 0 nitrates all the time then i would be concerned......i had that happen and then realized i was doing the test wrong. if you are using the test tube and bottle test than make sure you follow the instructions carefully. you have to shake this test to make it work right. if you don't it never gives a real reading. if you are using the strips then i would suggest getting the bottled tests, they are more accurate.

I am using the test tube kit. It showed nitrates when I was cycling the tank. It shows nitrates on the other tank I am cycling right now. It has always registered 0 on this tank and on the one I had previously (which is the one I'm now "re-cycling") once they were cycled.

[Northernguy]

Check the test kits manufacturing date.They have a 1yr shelf life.

[Gemini]

I often get very low, if any, nitrate readings on my community tank. There are a lot of plants, not too many fish, and I do at least 50% changes a week. So 0 is possible on a planted tank. If not planted I would be surprised.

[terrapin24h]

my moderately stocked 30 gal will show very low nitrate after 7 days, sometimes(i assume depending on how much i've fed)it won't show at all. I don't think i've ever gone past 10 days so i dunno about how long it would take. It's definitely possible though

--chris

[NickFish]

Very few of my tanks will ever read nitrates.

My planted tanks are so stuffed with greenery, my nitrates would ALWAYS be at 0 if I didn't add KNO3 to bring it back up. And yet, even though my nitrates are always at 0, I know I will still lose fish if I don't do water changes for a few weeks.
My reef tanks are always at 0 too, but don't do water changes for a few weeks, and again, you will lose fish.

Like I said, there is more to it than what we can test.

[Kaga's Kritters]

my tanks are not planted, i have never had luck with any plants, and don't want to put all that money into additives and special lighting and stuff, so i definitely have nitrates, but my water changes keep that under control. (dang tap water reads 10 nitrates normally though, so i do big water changes)

[Lady Hobbs]

Kinda like taking a bath in the same water over and over again. Gotta do those water changes.

[Jim101]

Does the size of the tank matter? I am setting up a 72g., so I would change out 50% every other week? Wouldn't the amount of fish drive that much of a change? Just wondering.... (really learning)

Thanks,

Jim

[Lady Hobbs]

Depends on what kind of fish you have, how much filtration you have and if it's planted or not.

[Northernguy]

Water changes is one of the most important parts of keeping a tank.
Its really is the same thing as rebreathing your own air.
I do water changes the old fashioned way on 4 tanks in 2 1/2 hours.
it really isn't alot of work once you get the hang of it.

[gourami*girl]

Another reason for no nitrates, even if your tank is not planted, is if you have brown diatoms or algae. My tank showed nitrates when it was new and clean, and now it's covered in brown diatoms and the nitrate reading is just above zero. The owner of my LFS (a very knowledgable guy) told me it's the diatoms.